A tubular string extending downhole can have a plurality of seats that accept objects, usually spheres, which land on discrete seats so that pressure can be built up and a downhole tool in that string operated. The balls can be the same or different sizes as are the corresponding seats. Regardless of the configuration it is desirable after operating the downhole tool to eject the ball from a given seat by a variety of known techniques and then to capture the balls. The reason capturing the balls is a benefit is that if left in the tubular string and there is a reversal in flow direction the balls can flow backwards and get wedged or jammed. Ideally, capturing the blown out balls will leave a main flow bore through a ball catcher to allow other tools to pass such as those that are supported on wireline or coiled tubing, to provide some examples.
In one design offered by Baker Hughes Incorporated in Catcher Sub Product Family 14077, the central tube catches ejected balls or darts and the differential pressure that develops pushes the ball or dart further into the central tube with flow possible around the central tube. The central tube has a hook feature to prevent escape of the dart or ball if there is a flow reversal. This design left the central passage obstructed which hampered or prevented subsequent operations further downhole from the Catcher Sub. U.S. Pat. No. 6,920,930 captures a ball when landed on a seat and then the seat with the ball breaks one connection and pivots on a remaining connection out of a central passage to allow a shifting sleeve to come down to keep the ball and the seat that traps it out of a main central bore. U.S. Pat. No. 6,732,793 shows a ball retaining device against reverse flow in a ball catcher that locates the captured balls centrally. U.S. Pat. No. 7,416,029 illustrates providing a tortuous path for a deformable ball that moves through a deformable ball seat.
U.S. Pat. No. 7,530,400 shows a ball catcher that has a main bore 18 that is split into two parallel bores 26 and 28 with an entry plate sloping at the top that has openings 38 and 40 aligned with bores 26 and 28 respectively. Only small balls will fit through hole 40 and pass through bore 28 unobstructed. Bigger balls 50 that go through hole 38 are captured at the bottom of bore 26 by a restriction 42, 44. If a small ball 52 goes down passage 38 and into bore 26, it has a way to get from bore 26 to bore 28 as those bores overlap to create a pass through channel so that the small ball 52 can get into bore 28 and escape. There are several issues with this design. First, if there is a flow reversal it will force the balls uphole and out of the ball catcher. Second, the way this ball catcher is set up with parallel bores, it has to have the channel between the bores because it has no way to insure the small balls will go in the pass through passage 28. Another disadvantage is that it has a pass through passage for one size of ball as opposed to catching all balls that enter. While it is recognized that the latter may simply be a design objective when a ball catcher is applied to a specific tubular string, it is recognized that in other applications, this feature can be less than ideal.
The present invention is a ball catcher that is designed to collect and store all the balls that reach its entrance in an annular storage location that surrounds a main bore so that the main bore is left open for other tools to later pass. The annular space preferably has a spiral guide slot that is small enough to prevent the balls being used from exiting the annular space but that advances such balls as they arrive to make efficient use of the annular space. Arriving balls get stopped at the inlet where flow around them displaces a seat that originally stopped the ball and allows the ball to advance past the seat and into the annular space where it stays trapped. These and other features of the invention will become more readily apparent to those skilled in the art from a review of the description of the preferred embodiment that appears below with the associated drawings while recognizing that the full scope of the invention is given by the claims that are attached below.